Ectomycorrhizal fungi are determinants of the success of pine regeneration in post-disturbance stands. These fungi promote resource acquisition and resistance in seedlings. They may alter plant chemistry in lodgepole pine (Pinus contorta var. latifolia), which may directly affect the success or failure of mountain pine beetle (Dendroctonus ponderosae) outbreaks in lodgepole pine stands of western Canada. It is unknown, whether the chemistry of pine seedlings differs on exposure to individual or a community of ectomycorrhizal fungi but could help to elucidate methods to promote healthy, post-disturbance regeneration. This project investigated such responses by examining induced monoterpene compounds as well as growth parameters of greenhouse-grown lodgepole pine seedlings whose roots were colonized by individual or a combination of ectomycorrhizal fungi. Ectomycorrhizal competition on artificial growth media was also assessed to support greenhouse findings. This research revealed that changes in ectomycorrhizal fungal species differently affect the induced chemistry of lodgepole pine depending on the fungal species, their interactions, and root colonization sequences. Considering the effects of these symbiotic fungi on plant growth and induced defenses, they can directly or indirectly affect the host tree susceptibility to their antagonistic biotic agents.

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